1. Technical Field
The present invention relates generally to tooth restoration, and more specifically to a tooth restoration post having a central dowel and filaments projecting therefrom.
2. Background Art
In restoring endodontically treated teeth, such as during a root canal procedure, posts are often used to support the core of the tooth, i.e., the part of the tooth that is either wholly restorative material or partially restorative material and partially tooth structure, that supports an artificial crown, direct or indirect restoration, or fixed-partial denture abutment. Presently, there are two types of posts, prefabricated and custom.
Ideally, a post should be well fitting, constructed with absolute minimal tooth structure removal, be strong, possess sufficient modulus of elasticity to absorb force and flex appropriately, reinforce and strengthen the root, utilize the canal irregularities for retention, be fabricated with minimal operator technique sensitivity, and arrest fractures and cracks within the root and prevent their extension into the periodontium. Custom posts and prefabricated posts each have some of these advantages, however they both have several disadvantages as well.
A custom post may be advantageous in that it attempts to reproduce the anatomy of the canal preparation created by the dentist to yield a post that fits the canal precisely. In other words, it is intended to be a xe2x80x9cpositivexe2x80x9d reproduction of the canal preparation (the xe2x80x9cnegativexe2x80x9d) within the root, that can be inserted passively, and that produces no insertional or functional stresses. Additionally, it may be used where prefabricated posts are ineffective due to the size and shape of the root canal.
However, custom posts also have several disadvantages. For example, it is time consuming to implement, requiring a minimum of two visits. An initial visit is required for the construction of an impression to manufacture the post, and a subsequent visit for the insertion of the post and preparation for the restoration after the post is inserted or cemented. It is also more costly since a laboratory fee is involved. A custom post also may require the removal of additional tooth structure to create a tapered preparation that will form and unobstructed path of insertion for the laboratory fabricated custom post. This tooth structure may be desired to support an already compromised tooth which will be further compromised by the removal of additional tooth structure. The tapered preparation may create a form that acts as a xe2x80x9cwedgexe2x80x9d that is conducive to future root fracture due to insertional and/or functional forces.
Further, creating and inserting a custom post is skill sensitive. If all the steps are not successfully accomplished, a less than appropriate product can result. For example, the post may provide less than adequate retention for the restoration, and/or be conducive to catastrophic root damage. Other disadvantages include a lack of support or reinforcement to the root, the necessity of removing all undercuts and irregularities created during root canal therapy, a possible compromise of esthetics, an inability to extend the product past root curvatures without perforation into periodontium (i.e., it must be a straight line), and an excessive enlargement of the root canal.
Conversely, prefabricated posts consist of solid dowels fabricated from various materials and generally do not accurately fit the canal into which they are inserted because the dowel is round and very few obturated root canals are round. Hence, supportive tooth structure frequently does not surround the prefabricated post on all sides. Additionally, the diameter of the canal often needs to be widened to create a preparation to accept a post surrounded by tooth structure on all sides. The widening can obliterate the canal space, and can substantially weaken the root or lead to iatrogenic perforation of the root.
Advantageously, a prefabricated post is less expensive than a custom post. Additionally, the prefabricated post can be constructed and inserted in a single visit. Further, a crown or bridge abutment can be prepared immediately after inserting the post, and installation is generally less sensitive to the technique and/or skill of the installer.
However, the prefabricated post also has several disadvantages. The tooth is fitted to accept the post, rather than the post being fitted to the preparation of the tooth. When a parallel design is used, which allows for a more benign distribution of forces than a tapered form, tooth structure in the narrowest and thinnest portion of the root must be removed. This weakens the root, increases the susceptibility of the root to fracture during insertion and/or function, and increases the potential for an iatrogenic perforation during preparation of the post space.
Further, when there is coronal destruction that extends into the root-orifice area, a prefabricated post will not fit this area accurately. The post will be surrounded by a void that must be replaced by a restorative or cementing medium. These media are not as supportive as tubular dentin. The longer the unsupported area, the longer the fulcrum arm that is created. In other words, the ratio of unsupported post area is increased in relation to post area supported by tooth structure. This has a weakening effect on the post and produces greater stresses during function than a post that is supported by tooth structure along its entire length. Therefore, this post may fit well in one area but be poorly adapted to the root in another area.
The prefabricated post also does not provide support or reinforcement of the tooth. Other disadvantages include the possible removal of undercuts and irregularities created during root canal therapy, compromise of the esthetics, an inability to extend beyond root curvatures (i.e., the rotary cutting instrument produces a straight line), and it may excessively enlarge the canal beyond the size created during the root canal therapy.
Accordingly, a need exists for a tooth restoration post and method that provide the advantages of both the custom and prefabricated posts while overcoming the disadvantages these posts.
The present invention overcomes the above-mentioned disadvantages and provides the advantages by providing an improved tooth restoration post and method. In particular, the invention provides a post having a central dowel with filaments projecting therefrom. The filaments can engage the walls of a canal to provide support to the tooth.
A first aspect of the invention provides a tooth restoration post, comprising: a central dowel; and a plurality of filaments projecting outwardly from the central dowel.
A second aspect of the invention provides a tooth restoration system, comprising: a post having: a central dowel; and a plurality of filaments projecting outwardly from the central dowel.
A third aspect of the invention provides a method of restoring a tooth, comprising: preparing a canal of the tooth; providing a post having a central dowel and a plurality of filaments projecting outwardly from the central dowel; and inserting the post into the canal of the tooth so that the plurality of filaments engage the walls of the canal.
The exemplary aspects of the present invention are designed to solve the problems herein described and other problems not discussed, which are discoverable by a skilled artisan.